Inter-user equipment (UE) transfer (IUT) transfers at the IP multimedia subsystem (IMS) level of all or some of the media flows and associated signaling between UEs. IUT for service continuity allows a multimedia session to be split on the local end across two or more UEs that are part of the collaborative session. FIG. 1 shows an example IUT operation. In FIG. 1, UE1 is running a multimedia session that comprises audio and video from a remote server. After IUT, the audio session is transferred to UE2 and the video session is transferred to UE3.
FIG. 2 is an example signaling flow for IUT operation. UE1 sends an IUT request to the service centralization and continuity (SCC) application server (AS) for transfer of the video session toward UE2 (12). The SCC AS sends a request to UE2 to establish an access leg on UE2, and updates the remote leg (14). The access leg is the call control leg between the UE and the SCC AS. The remote leg is the call control leg between the SCC AS and the remote party. The SCC AS sends an IUT response to UE1 (16), and the video session is transferred to UE2 (18). UE1 sends an IUT request to the SCC AS for transfer of the audio session toward UE3 (20). The SCC AS sends a request to establish an access leg on UE3, and updates the remote leg (22). The SCC AS sends an IUT response to UE1 (24), and the audio session is transferred to UE3 (26).
When media is split and transferred to two different devices, there may be a considerable lag between the first transferred media and the second transferred media (i.e., audio and video in FIGS. 1 and 2).